Geophysical studies was carried out at a proposed dam site across Osuworowo stream in Arochukwu, south eastern Nigeria to investigate the depth to bedrock, possible geologic structures and foundation conditions of the dam axis. The study area is located between latitudes 5°23.58”N and 5°23.707”N and longitude 7°53.93”E and 7°53.97”E. Its elevation ranges from 90 ft to 149 ft. Six Vertical Electrical Soundings (VES) were carried out along the stream course using ABEM SAS 1000 TERRAMETER and this was done using Schlumberger configuration with maximum half current electrode separation of 55m able to reveal deep seated structures. The ip2win software was used to model the VES data to give resistivities which vary between 258 Ωm and 39000 Ωm with three and four geoelectric layer combinations of sand, sandstone, sandyshale, shalysand and ale units. The high resistivities of the geoelectric layers sand thickness and dip showing high gradient in elevation differences are indications that the site is suitable for the dam construction. The geological result shows the presence of faults this is confirmed by change in strike and dip.
Magnetic Susceptibility Mapping and Depth Estimation of Anomalies were carried out on Igarra and its environs, Southwest Nigeria. This was to assist in mineral exploration in the area. The study area is located within the Igarra schist belt which is underlain by rocks of Precambrian basement complex. The Total Magnetic Field over the study area was obtained by digitizing the aeromagnetic map of Auchi (Sheet 226) acquired from the Nigerian Geologic Survey Agency (NGSA). A total of 19 (nineteen) magnetic anomalies were identified on the map; 5 magnetic highs and 14 lows. 8 anomalies have a NW-SE strike direction, 4 in the NE-SW and 7 in the E-W direction. The amplitude of the anomalies and strength of the total field were used to determine the susceptibility values for each of the anomalies. The Susceptibility values were used to generate a Magnetic Susceptibility map of the study area on SURFER 13 software. TMI plots on the anomalies were carried out on MICROSOFT EXCEL 2010. Depth estimates of the anomalies were got using three methods: The Half Width rule, Hannel rule and Tirburg rule. The Susceptibility map shows a noticeable pattern of increase in magnetic minerals from the Southwestern to the Northeastern part of the map. The Depth of the basement anomalies were relatively shallow ranging from 0.8 km to 2.6 km. The results of this work provide a preliminary guide to those that engage in mineral exploration / exploitation in the area.
The depositional Environment of Odoro -Ikpe, South East Nigeria was interpreted using pebble morphometry and sieve analysis. A field observation, sieve analysis and pebble morphometric analysis was carried out on the area which comprises of conglomerate, pebbles, sand stone and intercalation of shale's and clay. The lithofacies observed are lateralitic layer, pebbly sand, alternating layers of sand and conglomerates and layers of massive sand stone. The graphic mean and skewness of the grain size analysis shows that the sediments are very coarse which indicates a high energy environment. Graphic standard deviation gives a clue that the sediment were very poorly sorted, which is indicative of a fluvial deposit with high energy , while kurtosis result revealed very coarse sediment deposits. This implies that the particles were not transported very far. Pebble analysis shows the geometric forms and this was deduced from the plot on shape measurement triangle. The shape is compact bladed which is common with river deposits. The bivarate plot of mean diameter against standard deviation also indicated a fluvial environment as well as bivarate plots of co-efficient of flatness against sphericity and maximum projection sphericity against oblate, prolate index which comprises of river and beach environment. All results showed or indicated that the environment of deposition was of river.
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